1. Field of the Invention
The present invention relates generally to remote access devices, and more particularly to a steerable catheter having one or more stiffeners coextruded into the catheter shaft.
2. Description of Related Art
Modern medical practitioners frequently gain access to internal regions of a human or animal patient's body through the use of medical catheters in a variety of medical procedures. For example, medical catheters may be used to access internal body regions with a fiberoptic scope, light bundles, surgical instruments, medications, and/or other substances and devices, for a variety of diagnosis, treatment and/or material delivery purposes. These minimally invasive catheter access techniques can significantly reduce or eliminate the need for more invasive procedures.
Steerable catheters have been developed to provide improved access to remote sites such as internal body tissue. These catheters typically include a flexible catheter shaft and steering wires or other means for controlling the flexure of the catheter shaft. Steerable catheters find application in the observation and treatment of tissue in and around the joints in arthroscopic procedures, in and around the abdominal cavity in laparoscopic procedures, in spinal epiduroscopy, in the cardio-pulmonary and circulatory systems, and in other endoscopic procedures. Steerable catheters are also used for remote visualization and access in non-medical applications such as in the inspection and repair of internal engine components and other devices and structures.
A commonly encountered problem in the design of steerable catheters is the provision of acceptable flexibility of the catheter shaft, particularly near the shaft tip, while still maintaining adequate overall shaft stiffness for pushing through tissue openings and other access pathways. Difficulties are also encountered in providing a desired degree of stiffness to a catheter shaft formed from the relatively softer shaft materials that are often preferred for their trauma minimization qualities. Also, in most instances it would be desirable to provide a catheter shaft with a more “in-plane” steering bias for improved steering control, rather than a shaft that tends to twist or “pig-tail” out of the intended steering plane when steered. Another problem suffered by some previously existing catheter shafts is “socking”, wherein the shaft material crumples along the shaft's longitudinal axis when tension is applied to the steering wires, rather than bending along a smooth arcuate path.
Previously known methods of forming catheter shafts have also been found to have certain drawbacks. For example, some catheter shafts incorporate wire reinforcements encapsulated into their wall material or concentrically coextruded layers, which result in manufacturing difficulties and add considerably to the shaft's expense. In addition, the inclusion of wire within a catheter shaft may interfere with the guidance and placement of the catheter under flouroscopic observation, or may adversely impact regulatory approvals. Also, the material dissimilarities between the metal wire and the polymeric catheter shaft may result in slippage therebetween, possibly producing unpredictable steering characteristics. Welding shaft segments of differing durometer hardness together to form a catheter shaft also requires considerable effort and expense in ensuring proper alignment and connection between the segments.
Thus, it has been found that needs exist for an improved steerable catheter shaft and to related production methods. It is to these and other needs that the present invention is primarily directed.